This invention relates to centrifuges and, more particularly, to a centrifuge rotor having pivoted hangers whose orientation is controllable.
So-called cell washing centrifuges have been available for many years. In these centrifuges the material to be processed is placed in tubes positioned about a rotor which are permitted to swing outwardly towards a horizontal orientation during centrifugation at which time a washing fluid is introduced into the tubes. Following centrifugation, the tubes are then returned to a vertical orientation, locked in such vertical orientation, and the excess fluid decanted leaving the washed material in the bottom of the tube. This washing operation may be repeated several times.
Among the earlier centrifuges of this type is one disclosed in U.S. Pat. No. 2,739,759 issued March 1956 to Davidson et al. In this early cell washing centrifuge, the swinging tubes had to be removed from the centrifuge for decantation and then returned for further processing. This had many obvious disadvantages including being time consuming, requiring additional personnel for handling, and being susceptible to cross-contamination, breakage and the like. An improvement over this early centrifuge is disclosed in U.S. Pat. No. 3,401,876 issued September 1968 to Lucas. The Lucas system utilizes the centrifuge cover to vary automatically the tube orientation for filling, centrifuging and then decanting. During decanting the excess fluid is permitted to spill out over the top of the tube while the rotor is rotated at a somewhat lower speed than normal. Other systems have used various means including mechanical linkages, electromagnets and other positive actuators for controlling the orientation of the tube during the various operations. As might be suspected, most of these systems requiring positive actuators have been somewhat expensive, complex and are subject to breakdown and failure.
A rather simple system that provides excellent results is disclosed by Blum et al. in U.S. Pat. No. 3,420,437 issued Jan. 7, 1969. According to Blum et al. a locking ring is positioned axially of the rotor in either unlocked or locked positions to either permit or prevent the outward swing of the tubes during operation. While representing a vast improvement over the prior art, Blum et al. still required additional parts and required positive activation of the locking ring.
A still further effort using a passive system in this area is disclosed in U.S. Pat. No. 3,722,789 issued in Mar. 27, 1973 to Eugene R. Kennedy. According to Kennedy, a ball weight is placed in a J-shaped channel associated with each of the swinging tubes and the direction of rotation of the rotor shifted to either a clockwise or counter-clockwise direction to shift the tubes center of mass, under the influence of centrifugal force, and thereby reorient the tubes between the vertical and horizontal positions. Using this system the weight moves in the channel to alter the center of mass of the holder and thereby pivot the holder into the various desired positions. The disadvantage of this type of system is that the tube holders are relatively complicated and expensive. Therefore, the need still exists for a relatively simple method and apparatus for varying the positions of the tubes and/or buckets in swinging bucket centrifuges where the tubes are to assume different operating positions.
Accordingly, it is an object of this invention to obviate many of the disadvantages of the prior art swinging bucket centrifuges.
Another object of this invention is to provide an improved method for shifting the orientation of centrifuge tubes during operation.
A further object of this invention is to provide an improved apparatus for reorienting centrifuge tubes.